The Briggs and Stratton 303777 Vanguard is a 495 cc (30.2 cu·in) V-twin air-cooled four-stroke internal combustion gasoline engine, manufactured by Briggs and Stratton.
The B&S 303777 engine has an OHV (over-head valve) design and a vertical PTO shaft. This engine is equipped with float type, side-draft carburetor and a magneto electronic ignition system. The B&S 303777 engine used a full pressure lubrication system with spin-on oil filter.
The cylinder bore is 68.0 mm (2.68 in) and the piston stroke is 66.0 mm (2.6 in). The compression ratio rating is 8.2:1.
This engine produced 16.2 PS (11.9 kW; 16.0 HP) at 3,600 rpm of horsepower.
The breakdown of the engine code is as follows:
- 30 – Displacement
- 3 – Basic design series
- 7 – Vertical PTO-shaft
- 7 – Plain bearing, Pressure lubrication
- 7 – Electric starter
General information
Engine Specifications | |
Model | B&S 303777 Vanguard |
Type | 4-stroke, L-head, V-twin |
Displacement | 495 cm 3 (30.2 cu-in) |
Max. horsepower | 16.2 PS (11.9 kW; 16.0 HP) at 3,600 rpm |
Max. torque | – |
Fuel system | Float type, side-draft carburetor |
Cooling system | Forced-air |
Ignition system | Electronic |
Lubricating system | Full pressure lubrication with spin-on oil filter |
Starting system | Electric starter |
Fuel used | Gasoline |
Fuel tank capacity | – |
Cylinder Block and Head
Cylinder block | ||
Compression ratio: | – | |
Bore x Stroke | 68.0 mm X 66.0 mm (2.68 x 2.60 in) | |
Sleeve internal diameter | 68.000-68.030 mm (2.6772-2.6783 in) | |
Number of piston rings (compression / oil): | 2 / 1 | |
Side clearance | Top | 0.045-0.076 mm (0.0018-0.003 in) |
Second | 0.045-0.076 mm (0.0018-0.003 in) | |
Oil | 0.110-0.150 mm (0.0043-0.0059 in) | |
Ring end gap | Top | 0.200-0.400 mm (0.0079-0.0157 in) |
Second | 0.200-0.400 mm (0.0079-0.0157 in) | |
Oil | 0.200-0.400 mm (0.0079-0.0157 in) | |
Connecting rod small end ID | 17.090-17.100 mm (0.6728-0.6732 in) | |
Piston pin outer diameter | 17.070-17.080 mm (0.672-0.6724 in) | |
Cylinder Head | ||
Valve Arrangement: | OHV | |
Valves: | 4 (2 per cylinder) | |
Valve steam diameter | INTAKE | 5.950-5.960 mm (0.2343-0.2346 in) |
EXHAUST | 5.940-5.950 mm (0.2339-0.2343 in) |
Tightening torque
Tightening torque specs | |
Alternator (to cylinder) | 2.0 Nm; 1.5 ft·lb |
Air cleaner base (to carburetor) | 7.0 Nm; 5.2 ft·lb |
Air cleaner support bracket | 7.0 Nm; 5.2 ft·lb |
Alternator | 2.0 Nm; 1.5 ft·lb |
Armature | 3.0 Nm; 2.2 ft·lb |
Blower housings | 7.0 Nm; 5.2 ft·lb |
Back plate | 7.0 Nm; 5.2 ft·lb |
Breather | 3.0 Nm; 2.2 ft·lb |
Carburetor to manifold | 7.0 Nm; 5.2 ft·lb |
Connecting rod | 13.0 Nm; 6.9 ft·lb |
Crankcase cover | 17.0 Nm; 12.6 ft·lb |
Cylinder head | 19.0 Nm; 14.1 ft·lb |
Cylinder shield | 7.0 Nm; 5.2 ft·lb |
Exhaust manifold | 17.0 Nm; 12.6 ft·lb |
Flywheel nut | 175.0 Nm; 129.6 ft·lb |
Fan Retainer | 17.0 Nm; 12.6 ft·lb |
Governor lever nut | 8.0 Nm; 5.9 ft·lb |
Governor control bracket | 16.0 Nm; 11.9 ft·lb |
Intake manifold to cylinder head | 16.0 Nm; 11.9 ft·lb |
Oil pump | 7.0 Nm; 5.2 ft·lb |
Rewind starter (to blower housing) | 7.0 Nm; 5.2 ft·lb |
Rocker arm lock nut | 7.0 Nm; 5.2 ft·lb |
Rocker arm stud | 11.0 Nm; 8.2 ft·lb |
Starter motor | 16.0 Nm; 11.9 ft·lb |
Starter motor thru bolts | 6.0 Nm; 4.4 ft·lb |
Valve cover | 3.0 Nm; 2.2 ft·lb |
Service Information
Engine | |
Max speed | 3,600 rpm |
Valve clearance | |
Intake valve clearance | 0.10-0.15 mm (0.004-0.006 in) |
Exhaust valve clearance | 0.10-0.15 mm (0.004-0.006 in) |
Oil system | |
Oil type | API SF, SG, SH, SJ or higher |
Recommended oil | Summer: SAE 30, 10W-30 Winter: SAE 5W-30 |
Oil capacity (with filter) | 1.65 L (1.74 US. qt, 1.45 Imp. qt.) |
Ignition system | |
Spark plug | Champion RC12YC |
Spark plug gap | 0.7-0.8 mm (0.0276-0.0315 in) |
We try to use verified sources and official documentation, however, differences between sources or errors in entering information may occur. We do not provide advice on technical issues related to the engines operation or repair. We do not recommend using provided information for engines repairing engines or spare parts ordering, use only official service manuals and spare-parts catalogs.
Missing shaft length, keyway size, shaft diameter.
Where do I find the silly secret compression nos. for the Briggs & Stratton Model 303777 16 hp v-twin engine. I need to check its condition. Does it have a compression release for starting. How does that affect the cranking compression nos.? Thanks